1. Field of the Invention
The present invention relates to a recording medium, a production process and a heat-treatment process of the recording medium, and a recording apparatus. In particular, the present invention relates to a card-like unforgeable recording medium suitable for use in a credit card, bank card, prepaid card, clinic card, membership card or the like.
2. Related Background Art
Various information have heretofore been stored in cards such as credit cards, bank cards, prepaid cards, clinic cards and membership cards. An exemplary production process of such a card is illustrated in FIG. 14 and FIG. 15.
Namely, an overlay sheet 103 is laid on top of a core sheet 101 subjected to printing such as screen printing or offset printing. A magnetic tape 104 is arranged at a proper position on the overlay sheet 103 if necessary (FIG. 14). These sheets are melted to laminate each other under heating and pressure to unite them (FIG. 15). At this time, the surface of the resulting card is smoothed by pressing a metal plate having a smooth surface against the surface of the card.
A card-sized piece is punched out of this laminate to produce a card. Base materials (101, 103) for the card include vinyl chloride resins, PETG resins, ABS resins and the like having good melt lamination properties.
Methods for applying information to such a card include magnetization, embossing, bar coding or the like. Further, so-called optical cards can be used in which, by means of a laser beam, a part of an optical recording layer on an information recording medium is volatilized out, the reflectance of the optical recording layer is changed, or the optical recording layer is deformed, whereby information is recorded and reproduced by a difference in optical reflectance or transmittance, and the like. In recent years, IC cards referred to as chip cards, memory cards, microcomputer cards or electronic cards, in which an IC chip is installed, have begun to be used.
In the above-described methods, however, it is not easy to identify information stored in such a card as the owner""s own.
In general, uniform information such as logo prints, attention-requiring matters on use, agreements and an underground pattern or design are printed by the above-described screen printing or offset printing. However, such printing requires to make printing forms of the number of colors to be printed, and so it is difficult to make such forms for a short period of time, and a small quantity of production remarkably increases production cost.
In some cases, visible personal information, for example, a portrait and a name of an owner of a card, the available period of the subject matter of the card, etc., can be stored in the card. This can be achieved by adhering a photograph to the card or by printing with a sublimate-type thermal transfer printing system.
However, with the method in which the photograph itself is adhered to the card, it is difficult to make the card in a short period of time and at low cost.
The method using the sublimate type thermal transfer printing system has a drawback in that the cost of an ink ribbon used therefor is high, and so running cost becomes high. When full-color printing is conducted in particular, ink ribbons for 3 colors of yellow, magenta and cyan are always consumed irrespective of image density. Such a method is hence uneconomical. In addition, since such an ink ribbon is in the form of a thin film, it may have been broken upon its installation into a printer if an operator lacks experience. Further, there has been a limitation that a material suitable for the printing of the sublimate type thermal transfer printing system must be chosen for the surface of the card to be printed.
Since the printing is a contact type in which a printing head comes into contact with a printing surface of the card through an ink ribbon, in some cases, clean printing may not be obtained due to delicate irregularities on the printing surface, or printing failure may occur due to insufficient contact of the ink ribbon with the printing surface, if foreign matter such as dust is present on the surface of the card. In addition, there is a possibility that the printing head may come into contact with an end of the card when the printing is conducted up to the end of the card, and so the printing head may be damaged. Therefore, a blank is provided at the end of the card.
As a method for solving these problems, it has been proposed to provide an ink-receiving layer for ink jet on a surface of a card to conduct printing in accordance with an ink-jet recording method. According to this method, the above-described problem is avoided because this printing is a noncontact type in which a printing head does not come into contact with a printing surface.
There have heretofore been disclosed cards in which an ink-jet ink-receiving layer is laminated on a card substrate, and information is recorded on the ink-receiving layer by ink-jet recording. For example, Japanese Patent Application Laid-Open No. 64-43826 discloses a card in which an ink-receiving layer is laminated on a card substrate, and information is recorded on the ink-receiving layer by ink-jet recording.
Japanese Patent Publication No. 3-24906 discloses an ink-receiving layer comprising cationic aluminum oxide hydrate. Japanese Patent Application Laid-Open No. 2-276670 discloses an ink-receiving layer comprising alumina hydrate. Japanese Patent Publication No. 2-31673 describes a process for forming an ink-impermeable film on the printed surface of a recording medium after printing.
In recent years, forgery of information on a card for illegal use has become a social problem. The use of a card, in which a portrait of an owner of the card has been provided thereon, or personal information of the owner has been set forth thereon, should be useful for prevention of illegal uses. Even in such a card, however, additional information may be illegally recorded after regular recording. It is also difficult to identify the card as that having been issued from a regular origin of issue.
Additional recording may be conducted on the ink-receiving layer for ink-jet by ink-jet recording even after ink-jet recording is conducted. Further, additional printing may be conducted even in printing of the thermal transfer printing system. According to the method described in Japanese Patent Publication No. 2-31673, the ink-impermeable film is formed on the printed surface of the medium after ink-jet printing. Therefore, additional printing by ink-jet recording cannot be conducted. However, additional printing may be conducted by the thermal transfer printing system. Since no printing form is required for ink-jet recording, it is also easy to obtain a blank card to make a card in which forged information has been recorded. There is thus a demand for development of a measure to prevent such illegality.
It is an object of the present invention to provide an unforgeable recording medium, a production process and a heat-treatment process of the recording medium, and a recording apparatus.
The above object can be achieved by the present invention described below.
According to the present invention, there is provided a recording medium comprising a substrate and an ink-receiving layer provided on at least one side of the substrate, wherein a surface of the recording medium on the side that the ink-receiving layer is provided has irregularities or steps.
According to the present invention, there is also provided a process for producing a recording medium, which comprises laminating a plurality of substrate elements and heating the laminate under pressure, wherein a pressing member having irregularities or steps on a surface thereof is pressed against a surface of the laminate upon the heating.
According to the present invention, there is further provided a process for producing a recording medium, which comprises providing an uppermost layer of a thermoplastic resin on an ink-receiving layer and pressing a pressing means having irregularities or steps on a surface thereof under heating against the uppermost layer, thereby forming irregularities or steps on the uppermost layer.
According to the present invention, there is still further provided a process for heat-treating a recording medium having a substrate, an ink-receiving layer provided on at least one side of the substrate and an upper layer composed of thermoplastic resin particles capable of making the upper layer nonporous by heating and provided on the ink-receiving layer, comprising pressing a pressing means, the surface of which has partially nonuniform physical properties, against the upper layer, thereby making the upper layer nonporous and at the same time forming irregularities thereon.
According to the present invention, there is yet still further provided a recording apparatus comprising an ink-jet recording unit and a pressing means, the pressing means serving to heat-treat a recording medium by bringing the pressing means into contact under pressure with the surface of the recording medium after ink-jet recording and being equipped with a means for forming irregularities on the surface of the recording medium, and having a mechanism for aligning the recording medium toward a rotating and feeding direction of the pressing means, a mechanism for detecting the recording medium to be fed to the pressing means, a mechanism for detecting a rotational phase of the pressing means, and a mechanism for controlling the rotational phase of the pressing means or/and the position of the recording medium so as to form irregularities at the prescribed positions of the recording medium by analyzing a signal from the medium position detecting mechanism and a signal from the rotational phase detecting mechanism.
The irregularities or steps are scarcely observed in an ordinary state and do not affect the design of the resulting card. However, the irregularities or steps on the surface can be observed in relief by obliquely observing the card or irradiating the card with light to observe the reflected light. In addition, printing of the thermal transfer printing system cannot be beautifully conducted due to the irregularities or steps on the surface of the card, and so additional printing is substantially infeasible. Further, information can be given by varying irregularities or steps. For example, steps are provided so as to relieve the logo print of an issuer, thereby identifying the issuer, which is useful for prevention of forgery.
When printing of the thermal transfer printing system is conducted thereon, a transferred condition of a thermal transfer ink is changed at steps, and so the information printed is relieved to prove the additional printing. Therefore, the steps are useful for prevention of forgery.